Having problems running when car reaches operating temperature. I can see in the clear filter before the carb and it is like it stays full of gas until the car warms up and then the carb starves for fuel. Have ruled out vapor lock and ran all new fuel lines. I have replaced the fuel pump and even varified no blockage at the tank. I put on a friend's new carb and it made no difference so I don't think it is dirt or floats.

Any ideas??? I don't know can it be vacuum or what are the options since it is only when at operating temp? No problems cold.

Your pump is sucking air from somewhere. Either a leak in the line or an interally leaking pump. Make sure your fuel line is not getting overheated.
Jim

I re-routed and wrapped the lines and even wrapped the headers, nothing feels warm running. All the lines are 3/8" aluminum with braided stainless going in to and exiting pump. Running a phenolic spacer on carb. It has reacted the same with old and new lines and two fuel pumps.

Sounds like the only thing you have not changed is the tank. You may have a crack in the tank tube. Pay special attention to the rubber tubing at the tank. You could drop the tank and change the sending assembly. There is no miracle fix. It's a very simple system. Three components, tank, lines pump. It has to be one of the three. A pressure gage can be a good tool to diagnose with.
Jim

runs the same when I hooked up a line directly from a gas can to the fuel pump.

Is that a '67 with the '67 intake manifold?

Q

'74 pontiac 350 with Edelbrock
performer intake.

Yo! Guys, back home! Anyway, you say it's starved for fuel. Let's go step by step. First, describe starved for fuel. While in neutral, does it sputter at idle upon acceleration, or is it when the car is under load. You have to get a clear picture out. It's just like saying the car won't run: Does "won't run" mean that it cranks but won't start, or it won't crank. Likewise, starved for fuel doesn't give up much to work with. As a reslut you get a series of answeres that you have received.

(Another quite important peice of information that would help is to know whether this is a new car/set-up for you, meaning that you don't know how it ran before, or you have had the car, it ran properly before, and this is a new problem.)

To eliminate email tag, you say that you verify gas at the filter. You have ruled out such a problem with other carbs; even so, you make better headway by knowing for sure that the carb has gas. Physically check the fuel bowl for gas. (Something tells me that you have a Holley on it. I dislike Holleys, so I'm biased and, natrually would say that the Holley is the problem. If you want a car that runs, put a Quad on it.)

That manifold doesn't help. Unless there is something in the 21st century production, countless flow test have proven that Pontiac's stock manifold is the best manifoild.


Because life is complicated, let's keep it that way: Could it be a weak coil?

I will check coil. As posted, when it warms up I can see the clear filter before the carb start filling with air and then it will eventually run empty and the car will die. Only happens when the car reaches operating temperature.

Please explain your thoughts on the coil.

P.S.
Had car two years and it ran fine until this year. Haven't changed any parts to cause a change prior to this issue. Also was running a Carter and borrowed a Holley to verify there wasn't something wrong with my carb I was missing.

When my car is cold , fuel filter shows gas in it, when hot, and running it shows no gas, but car runs...

Sounds like what mine does, but it will actually stop running.

i agree with checking the carb itself for fuel. my clear filter looks nearly empty most of the time too, and it runs... rich (carb) with no stalling. also check fuel pressure psi. start checking things like you would if you didn't have a clear filter. it is possible it could be deceiving you. ignore it and start your diagnosis again maybe?

If you happen to have the carb apart, see if the needle valve sticks or if it opens easilly. I'd replace it just to be sure, regardless of which carb you run.

One thing I did want to find out ... does the car stall under all conditions when it's warm? Or does it only stall out when it is idling?

Are you sure you put the fuel pump lever UNDER the eccentric?

Q

How do I verify it is under the eccentric? I couldn't feel it after I had it hooked on due to lack of room. I assumed if it ran fine cold it was working o.k.

One more idea. Is this with a quadrajet? If so, can you tell me how much effect the idle mixture screws have? In other words, if you close the idle mixture screws all the way does the engine immediately die, or does it lumber on? (If it's not a Q-Jet but rather a Holley the symptoms might be the same, but the solution is different.)

Also, when you "blip" the throttle, do you get a puff of black smoke out the pipe?

I know you think the motor is starving for fuel, but is might be the opposite.

Q

I am running a Carter 750 and even put on a friends Holley 600 and it ran the same. Don't notoce smoke.

does your fuel pump pressure drop when it gets warm? what psi are you reading before and after? if the psi is the same, check volume before and after by pumping fuel in a measured cup for a set amount of time. there is a volume spec somewhere, but i dont know what/where it is.

have you checked running it w/o the gas cap? may sound funny , but you might get vacuum....

When I replaced my pump awhile back, the fuel level in the filter did not drop as radically as before when the engine warmed up. But, I guess he has another problem.

Ran without cap on and directly from a can to pump also and same thing. Someone mentioned coil, I have concerted over to standard HEI if that matters.

Is the standard HEI you converted to rebuilt,new or did you slap on one from a wrecker? Also what is the condition of the battery cables? Are they clean/tight at the starter? My car was having the same problem and i had the same thing happening in my fuel filter but it ended up being the batery cables.Just a thought.the whole time i was thinking fuel related.Then i ruled that out,when it wouldn't start/run hot or cold.

David

sounds to me like you had a weak spring in the old fuel pump, hit a hard acceleration, bent the push rod, and now it is sticking when it heats up and expands in the block.
it is the only thing left that it could be.

All new parts for the HEI, performance advance weights and springs, cap and rotor. Will definitely check battery cable since replaced starter last year.

Also, what operating temp is everyone running at?